What Is The Megastructure Star That Astronomers Are Worried About? Nobody Can Explain Its Dimming Behavior

For over a year now, scientists have been trying to figure out what the hell is going on with star KIC 8462852. The “megastructure” star has been dimming in strange ways, and now they’ve found that it’s also been fading significantly over time. Researchers have come up with a variety of explanations from KIC 8462852’s unusual behavior, from “There’s a planet in the way” to “ALIENS!”, but none of them fully explain why this weirdo star just keeps getting weirder.

KIC 8462852, which also goes by the name “Tabby’s Star,” was first observed by the Kepler space observatory after its launch in 2009. For four years, Kepler monitored more than 150,000 stars, looking for dips in brightness that would suggest the existence of exoplanets (planets that orbit stars other than our sun). The logic was that a star’s brightness would dim when a planet crossed in front of it, and a regular sequence of dimming could indicate a planet orbiting around that star. Scientists and observers have found thousands of exoplanets by analyzing Kepler’s data and looking for this periodic dimming.

According to Slate, KIC 8462852 is “more massive, hotter, and brighter than the Sun,” but it’s too far away from Earth to see without a telescope. In 2011, observers found that KIC 8462852 was dimming, but not in the way of most stars orbited by exoplanets. KIC 8462852’s drops in brightness were erratic and extreme, sometimes dipping by 15 and 22 percent. To put that in perspective, a massive planet like Jupiter passing in front of KIC 8462852 would only block one percent of the star’s light. So what could possibly be causing the star to dim by 22 times that amount?

And if that weren’t strange enough, new research suggests that, in addition to the inexplicably extreme and irregular dips in brightness, the star has been fading steadily over a number of years. According to Kepler data, from 2009 to 2012, KIC 8462852 faded by one percent. Then, the star suddenly dimmed by 2 percent in six months, and then held steady for the following six months. Previous research suggests that the star may have been dimming since the late-19th century, fading by 14 percent from 1890 to 1989. “The steady brightness change in KIC 8462852 is pretty astounding,” Ben Montet, co-author of the most recent study, said in a statement. “Our highly accurate measurements over four years demonstrate that the star really is getting fainter with time. It is unprecedented for this type of star to slowly fade for years…."

Having ruled out tech malfunctions as an explanation for the star’s behavior, scientists have struggled to come up with a convincing story of what’s going on with KIC 8462852. In a paper last year, Yale scholar Tabetha Boyajian suggested that another star passing near KIC 8462852 could have dragged a horde of comets in toward the star that would block its light. Montet and co-author Josh Simon think that the fading they’ve observed occurring over a period of months could have been caused by debris from “a collision or breakup of a planet or comet in the star's system” blocking the star’s light. But none of these explanations account for the slow fading of the star that may have been occurring for more than a century.

Surely the most entertaining (if not the most likely) theory comes from Penn State astronomer Jason Wright, who suggested last year that the star’s dimming could be caused by a “swarm of megastructures” meant to harness a star’s energy. “I was fascinated by how crazy [the date] looked,” Wright told The Atlantic. “Aliens should always be the very last hypothesis you consider, but this looked like something you would expect an alien civilization to build.” Such megastructures could form the massive theoretical structure known as a Dyson Sphere. Because I’m a huge nerd, I’ll let Captain Jean-Luc Picard explain it to you:

In the twentieth century, a physicist called Freeman Dyson, postulated the theory that an enormous hollow sphere could be constructed around a star. This would have the advantage of harnessing all the radiant energy of that star. Any population living on the interior surface would have virtually inexhaustible sources of power.

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As exciting as it is to imagine that KIC 8462852 is dimming because an extremely advanced alien civilization is building megastructures to use its energy, that’s (sadly) probably not what’s going on. Jeffrey Kluger at Time commented skeptically,

If you’ve got a half a dozen natural scenarios that you reject as implausible and then an additional one that requires giant light-concentrating spacecraft built by aliens, and that’s the one passes your plausibility test, well, you might not have evaluated the probabilities as carefully as you should have.

Waah-waah. Scientists will no doubt continue to explore what might be happening with this bizarrely-behaving star, but in the meantime, let’s just pretend it’s aliens, OK? It’s more fun that way.